Doctors tell us that good eating habits and regular exercise is practising preventive medicine because these habits keep us healthy. The same is true for your lawn because by keeping it healthy you eliminate conditions that are favourable for weeds to grow and for disease to develop. Keep your lawn thick and healthy so there is no space for weeds.
Take a walk around your lawn and notice its overall appearance. Are some areas doing better than others? For example you might find patches of thick turf in the front yard that runs into less healthy or weed-filled areas along the side of the house. Perhaps there is one area where grass never grows no matter how much fertilizer you apply. Or you might find moss where grass never seems to grow on the south side of the house in a damp area shade by a large tree. Part of your lawn that is choked with weeds might be downwind of a vacant block that is filled with weeds etc. The point of all this is there is a reason for the success and failure of your lawn in these areas. Much of its success depends on type of soil (where the lawn is), how much sun it gets, and the amount of water and nutrients it receives.
PH of Your Lawn
Lawns usually prefer a slightly acidic or neutral soil.
Check the pH, the acidity or the alkalinity of the soil, by using a simple pH test kit.
If a test result is between 6.5 and 7 you need do nothing because that range is ideal for lawns. But a 5.5 result means the soil is slightly acidic, and probably needs “sweetening”.
If the soil is too acidic
Add lime and dolomite. In this case dolomite is preferred because it also contains magnesium. And magnesium is necessary for plants to produce chlorophyll that allows them to produce energy. Most Australian soils are deficient in magnesium and it’s readily leached from the soil, so dolomite has a double action.
Lime on a heavy clay soil helps break it down from really heavy clods, so that it becomes crumbly. This makes the soil easier to work, and also aids root penetration deep into the soil.
As a rule of thumb, apply a handful of dolomite per square metre. But for highly acidic soil, double the amount, then water it in.
Many lawn problems are caused by soil compaction, as people and vehicles repeatedly move over the lawn. Wet soils are especially prone to compaction. If your lawn is not healthy and green, and is full of weeds, the whole lawn may need treating for soil compaction. Test for compaction by thrusting a garden fork into the ground. If the fork won’t go in at least half way down the tines, the soil is compacted.
To relieve compaction for small lawns a simple garden fork can be used to aerate the soil. Work the fork backwards and forwards at approximately 10 cm intervals to open up the soil. On larger lawns it may be worthwhile using a coring or aeration machine